I am taking a real-time
fft of an audio signal using
fftw library. I take the output of the
fftw signal on $y$-axis and plot it against the linear frequency bins on $x$-axis.
I've noticed that spectrum analyzers use a skewed
plot(log plot). I can get my $y$-axis (
magnitude) into $\rm dB$ by doing
20*log(magnitude) but I don't know how to get my frequency axis($x$-axis) into log-scale. I need some help in doing that in C/C++ not Matlab.